Furnace Distribution Research Articles

3D high-quality temperature-field reconstruction method in furnace based on acoustic tomography

Reconstructed 3D high-quality temperature distribution in furnace can provide important information to better control boiler operations and to optimize the combustion process. Acoustic travel-time tomography is considered to be a promising method that uses the dependence of sound speed on temperature to reconstruct the temperature field. In this paper, a new 3D temperature field reconstruction method based on radial basis function approximation with polynomial reproduction (RBF-PR) and truncated generalized singular value decomposition (TGSVD) is proposed to solve the inverse problem. To improve the reconstruction quality, we consider the refraction effect of sound waves in the non-uniform temperature field and estimate the sound wave propagation path model in the reconstruction method. The shooting method with improved Powell algorithms is used to solve the propagation path model and obtain the relationship between the acoustic travel-time over the propagation path and temperature distribution. Simulations are implemented to evaluate the effectiveness of the proposed reconstruction method. The results indicate that compared with other methods, the new reconstruction method that considers the refraction effect can reconstruct temperature distribution with higher accuracy and better anti-noise ability. Experimental results also demonstrate that the temperature distribution can be reconstructed effectively by the proposed method.

Energy Efficient and Sustainable Design and Development of Muffle Furnace for Melting Alloys

Energy efficient furnace for melting of alloys is crucial requirement for an industry for sustainable growth. An enclosed structure in which material can be heated to very high temperatures for melting metals. In this work authors have made attempt to design and develop energy efficient electrical muffle furnace for melting of aluminium alloys which provides even heat distribution in furnace with help of cylindrical shaped muffle. Muffle along with an electrical resistance wire coil in the chamber walls are heated and heat the metal of that chamber radiantly by all of the side, so that the material being heated has no acquaintances with flame. Designing of muffle furnace has based on material to be melt and melting temperature. Recently most of muffle furnaces are having square or rectangular shaped muffle but in this type of muffle even heat distribution cannot be achieved. With the proposed design electricity consumption target is approximately 2.5 KW in less time for designed specification environment, which is lesser than commercial furnaces. Hence, heating time of metal and cost of these type of muffle furnace has enormously reduces than furnace which is currently available in the market. With less consumption of energy for same heat output leads the path for sustainable manufacturing of casting also.

Numerical and Experimental Study on the Effect of Over Fire Air on NOx Distribution in Furnace

In this paper, a numerical investigation and experimental study was used to research the effect of a power plant 600MW supercritical four walls tangentially fired boiler furnace over fire air opening size on the inside furnace NOx concentration distribution and the results coincide. There are four cases in all. The influence and formation of NOx that was produced by pulverized coal furnace during combustion processes were analyzed. The research was proved that the over fire air has great effect on the concentration distribution of NOx in the furnance.

Numerical Study of the Gas Distribution in an Oxygen Blast Furnace. Part 1: Model Building and Basic Characteristics

Based on multifluid theory, transport phenomena theory, metallurgical reaction kinetics, thermodynamics, and computational fluid dynamics, a multifluid model for an oxygen blast furnace was established to evaluate the gas distribution in a furnace. The uneven distribution of recycling gas in oxygen blast furnaces was found to be a severe problem. This uneven distribution resulted from injecting a large amount of recycling gas into the furnace shaft. Gas distribution substantially affects the energy and heat utilization of an oxygen blast furnace. Therefore, the basic characteristics of the gas distribution in an oxygen blast furnace are illustrated. The results show that in the top of the oxygen blast furnace, the concentration differences of the CO and CO2 between the center and edge reach 7.8% and 11.7%, respectively. The recycling gas from the shaft tuyere only penetrates to two thirds the length of the radius.

Optimizing calculation of particle size distribution of feeding coal for circulating fluidized bed boiler

The particle size distribution (PSD) of feeding coal affects the solid concentration distribution, combustion fraction distribution and coal combustion behaviors in the circulating fluidized bed (CFB) boiler. In engineering, the particle size distributions for different feeding coals are determined empirically, such as the mean particle size of anthracite is smaller, and the mean particle size of lignite is larger. But the specific research on the PSD of different feeding coal is still lacking. In the operation of CFB boiler, the PSD of feeding coal is not adjusted. By optimizing the particle size distribution of feeding coal to adjust the mass ratio of fine particles in the dilute zone and coarse particles in dense zone, it is possible to obtain a good solid concentration distribution in the dilute zone and to improve coal combustion performance. This can assure the output of boiler and reduce the carbon content in ash, as well as reduce the friction of boiler and energy consumption of the fan. In this paper, an optimization model of the PSD of feeding coal of CFB boiler was developed, by setting the solid concentration of the furnace outlet and the mean retention time of coarse feeding coal in the furnace as the optimization goal. This procedure is based on the experimental results of primary fragmentation, burnout and ash formation of coal, using wen-chen hydrodynamic model. The optimized PSD of feeding coal had been calculated in some bed inventory, which results in an optimum solid concentration distribution in furnace and lower carbon content in bottom ash. Before and after optimization results showed that when the bed pressure drop was 11.3 kPa, the carbon content in bottom ash was reduced from 2.14% to 0.77%, and the solid concentration in the furnace outlet increased from 2.6 kg/Nm3 to 2.71 kg/Nm3. The calculation accuracy of the model was validated in a1060 t/h CFB boiler.

Experimental investigation on simultaneous measurement of temperature distributions and radiative properties in an oil-fired tunnel furnace by radiation analysis

The paper reports experimental investigations on simultaneous measurement of temperature distribution and radiative properties in an oil-fired tunnel furnace by radiation analysis. Two color CCD cameras were used to obtain visible thermal radiation in the furnace. A radiation imaging model was established by the calculation of radiative transfer equation in the furnace. The temperature distribution and radiative properties can be obtained from the inversion of the radiative imaging model. The validity of radiative imaging model was verified by the numerical analysis of cavity radiation and isothermal system radiation, and the accuracy of reconstruction method was validated by simulation reconstruction. The experimental analysis was divided into two parts. Firstly, the temperatures of wall surface were calculated from the radiative image of refractory wall and compared with the measured temperature of a thermocouple. The difference between the two methods was only about 20 K. Secondly, the temperature distributions in the furnace, absorption coefficients of combustion medium, and emissivities of refractory wall were reconstructed. Because of a single burner in the tunnel furnace, the temperature distributions in the XY vertical sections in the furnace were with temperature higher in the center and lower near the refractory wall surface, and the temperatures decreased along the length of the tunnel furnace. The measured emissivity of refractory wall showed that the refractory material of RPA-MC30 is with high reflectivity in visible spectrum.

Simulation study on reconstruction model of three-dimensional temperature distribution within visible range in furnace

This paper presents a reconstruction model of three-dimensional temperature distribution in furnace based on radiative energy images captured by charge-coupled device (CCD) cameras within the visible wavelength range. Numerical simulation case was used in this study and a zigzag eccentric temperature distribution was assumed to verify the model. Least square QR-factorization (LSQR) method was introduced to deal with reconstruction equation. It is found that the reconstructed temperature distributions in low-temperature areas had some fluctuations and high-temperature areas were reconstructed well. The whole reconstruction relative error was mainly due to errors in low-temperature areas and the relative error for highest-temperature reconstruction was quite small.

무촉매 환원법이 적용된 응용 재연소 방법에 의한 NOx와 CO의 저감 효과

From the view of the environmental protection against the use of fossil fuels, the great of efforts have been exerted to find an effective method which is not only pollutant reduction but also high thermal efficiency. Reburning is a useful technology in reducing nitric oxide through injection of a secondary hydrocarbon fuel. In this paper, an experimental study has been conducted to evaluate the hybrid effects of reburning and selective non-catalytic reaction (SNCR) on NOSUBx/SUB/CO reduction from oxygen-enriched LPG flame. Experiments were performed in flames stabilized by a co-flow swirl burner, which was mounted at the bottom of the furnace. Tests were conducted using LPG gas as main fuel and also as reburn fuel. The paper reported data on flue gas emissions, temperature distribution in furnace and various heat fluxes at the wall for a wide range of experimental conditions. Overall temperature in the furnace, heat fluxes to the wall and NOSUBx/SUB generation were observed to increase by oxygen-enriched combustion, but due to its hybrid effects of reburning and SNCR, NOSUBx/SUB/CO concentration in the downstream has considerably decreased.

Two-stage numerical simulation for temperature profile in furnace of tangentially fired pulverized coal boiler

Considering the fact that the temperature distribution in furnace of a tangential fired pulverized coal boiler is difficult to be measured and monitored, two-stage numerical simulation method was put forward. First, multifield coupling simulation in typical work conditions was carried out off-line with the software CFX-4.3, and then the expression of temperature profile varying with operating parameter was obtained. According to real-time operating parameters, the temperature at arbitrary point of the furnace can be calculated by using this expression. Thus the temperature profile can be shown on-line and monitoring for combustion state in the furnace is realized. The simulation model was checked by the parameters measured in an operating boiler, DG130-9.8/540. The maximum of relative error is less than 12% and the absolute error is less than 120 °C, which shows that the proposed two-stage simulation method is reliable and able to satisfy the requirement of industrial application.

Application of Sequential Quadratic Programming Method to Temperature Distribution Control in Reactor Furnace

Recently, various studies have been undertaken to examine the inner furnace phenomena of a blast furnace. These studies are limited, however, to the evaluation of furnace performance while a designed method of furnace control remains unfulfilled. This paper proposes a method of estimating temperature distribution in a reactor furnace using boundary data in order to control inner target furnace temperature distribution. Initially, a simplified furnace simulation program for the calculation of inner furnace gas flow, pressure and temperature distribution is developed. Following that, the simulator is used to estimate and control inner furnace temperature distribution. In the estimation, boundary data such as temperature and pressure, measured near a furnace wall, are used in the furnace simulation. Then, for the control of inner furnace temperature distribution, necessary values for gas blowing at the bottom of the furnace and the burden supply at the top of the furnace are used. Both for the estimation and the control of the inner furnace temperature distribution, a sequential quadratic programming method, a method of the iterative optimization, is applied. In our method, an estimation of inner furnace temperature distribution is done as preparation for the determination of furnace control variables. Through numerical experiments, the validity of our method is demonstrated, showing that the temperature distribution in a furnace can be regulated to the desired one after iterative control operations.

Effects of Addition of Carbon Dioxide on Thermal Characteristics in Oxygen-Enriched Hydrogen Flame

An experimental study has been conducted to evaluate the effects of CO2 addition on thermal behavior in oxygen-enriched hydrogen flame. Experiments were performed on flames stabilized by a co-flow swirl burner, which was mounted on top of the furnace. Several different oxidizer compositions were prepared by volumetrically replacing N2 by CO2. In a steady state, the total as well as radiative heat flux from the flame to the wall of furnace has been measured using a heat flux meter. Temperature distribution in furnace has been also measured and compared. By increasing CO2 proportion in the oxidizer, the convection became to play a more significant role rather than radiation due to heat blockage effect. Overall temperature in the furnace was seen to decrease, while the total heat flux has increased.

이산화탄소가 수소 산소부화 화염의 열전달에 미치는 영향

An experimental study has been conducted to evaluate the effects of CO₂ on heat transfer from oxygen-enriched hydrogen flame. Experiments were performed on flames stabilized by a co-flow Swirl burner, which was mounted on top of the furnace. Five different oxidizer Compositions were prepared by replacing Nz With CO2- In a steady state, the total as well as radiative heat flux from the flame to the wall of furnace have been measured using a heat flux meter Temperature distribution in furnace also has been measured and compared. By increasing CO₂ proportion m the oxidizer, the convection played a more significant role rather than radiation. Overall temperature in the furnace was seen to be decreased, while the total heat flux has increasedbr/

D206 SIMULATION ON AN OPTIMAL COMBUSTION CONTROL STRATEGY FOR 3-D TEMPERATURE DISTRIBUTIONS IN PC-FIRED UTILITY BOILER FURNACES

The 3-D temperature distribution in a utility boiler furnace is essential for the safe, economic and clean operation of PC-fired furnaces with multi-burner system. In the past, due to the lack of applicable techniques to monitor the 3-D temperature distributions in furnaces, it is difficult to improve the control quality for the combustion processes. The authors is now establishing a technique to visualize 3-D temperature distributions in PC-fired furnace, which makes it possible to study a new combustion control strategy. In this strategy, the whole height of the furnace is divided into several parts, and the average temperatures, the bias magnitudes of the flame centers in the two axis of the horizontal plane in every part is extracted from the visualization results of the 3-D temperature distributions. A linear model is set up to relate the features of the temperature distributions with the input of the combustion processes, such as the flow rates of fuel and air fed into the furnaces through all the burners. The genetic algorithm is adopted to find the optimal combination of the whole input parameters which ensures to form an optimal 3-D temperature field in the furnace desired for the operation of boiler. Simulation results show that the strategy can soon find the factors causing the temperature distribution apart from the optimal state and give correct adjusting suggestions.

Vision-based measurement of temperature distribution in a 500-kW model furnace using the two-colour method

This paper describes the design and evaluation of a novel optical instrumentation system that has been developed for the on-line continuous measurement of temperature distribution in a furnace. The system comprises optical filters, a CCD camera, a frame-grabber and associated software. Based on the two-colour method, the average temperature of the flame field is calculated from the ratio of averaged grey levels of the two images alternatively captured at two different wavelengths. Accordingly, a pseudo-instantaneous temperature distribution is obtained from a single-wavelength image and presented by pseudo-colour. Experimental results obtained from a 500-kW model furnace show that the temperature distribution ranged from 1331 to 1606°C for coal-fired flames and from 1156 to 1358°C for gas-fired flames. A continuous monitoring of the temperature distribution in the furnace has also been performed over a period of 100 min. A comparison between the results measured by the system and those from a conventional pyrometer demonstrates that the system is capable of measuring the temperature distribution with a reasonable accuracy.

99/02298 Development of coal feeding system for coal gasifier: Kim, J. G. et al. RIST Yongu Nonmun, 1998, 12, (2), 146–153

The particle size distribution (PSD) of feeding coal affects the solid concentration distribution, combustion fraction distribution and coal combustion behaviors in the circulating fluidized bed (CFB) boiler. In engineering, the particle size distributions for different feeding coals are determined empirically, such as the mean particle size of anthracite is smaller, and the mean particle size of lignite is larger. But the specific research on the PSD of different feeding coal is still lacking. In the operation of CFB boiler, the PSD of feeding coal is not adjusted. By optimizing the particle size distribution of feeding coal to adjust the mass ratio of fine particles in the dilute zone and coarse particles in dense zone, it is possible to obtain a good solid concentration distribution in the dilute zone and to improve coal combustion performance. This can assure the output of boiler and reduce the carbon content in ash, as well as reduce the friction of boiler and energy consumption of the fan. In this paper, an optimization model of the PSD of feeding coal of CFB boiler was developed, by setting the solid concentration of the furnace outlet and the mean retention time of coarse feeding coal in the furnace as the optimization goal. This procedure is based on the experimental results of primary fragmentation, burnout and ash formation of coal, using wen-chen hydrodynamic model. The optimized PSD of feeding coal had been calculated in some bed inventory, which results in an optimum solid concentration distribution in furnace and lower carbon content in bottom ash. Before and after optimization results showed that when the bed pressure drop was 11.3 kPa, the carbon content in bottom ash was reduced from 2.14% to 0.77%, and the solid concentration in the furnace outlet increased from 2.6 kg/Nm3 to 2.71 kg/Nm3. The calculation accuracy of the model was validated in a1060 t/h CFB boiler.